Inkjet printer having a printhead with a bi-layer thermal actuator coil

ABSTRACT

Provided is a printhead for an inkjet printer. The printhead has a plurality of micro-electromechanical ejection mechanisms arranged in a wafer substrate, with each mechanism having chamber walls and a roof formed on top of said substrate to define an ink chamber. One wall of the chamber defines a slot therein. The mechanism also includes an ink supply channel defined through the substrate to said chamber. The mechanism includes a bi-layer thermal actuator coil fast with the substrate and ending in a strut extending through the slot, said strut fast with a paddle device within the chamber.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/056,146 filed Feb. 14, 2005, now issued U.S. Pat. No. 7,390,421,which is a continuation of U.S. application Ser. No. 09/113,076 filedJul. 10, 1998, now issued U.S. Pat. No. 6,855,264, the entire contentsof which are herein incorporated by reference.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, US patent applications identified by their US patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the US patent applications claim the right ofpriority.

CROSS- REFERENCED AUSTRALIAN US PATENT/PATENT PROVISIONAL APPLICATION(CLAIMING PATENT RIGHT OF PRIORITY APPLICATION FROM AUSTRALIAN NO.PROVISIONAL APPLICATION) DOCKET NO. PO7991 6,750,901 ART01US PO85056,476,863 ART02US PO7988 6,788,336 ART03US PO9395 6,322,181 ART04USPO8017 6,597,817 ART06US PO8014 6,227,648 ART07US PO8025 6,727,948ART08US PO8032 6,690,419 ART09US PO7999 6,727,951 ART10US PO80306,196,541 ART13US PO7997 6,195,150 ART15US PO7979 6,362,868 ART16USPO7978 6,831,681 ART18US PO7982 6,431,669 ART19US PO7989 6,362,869ART20US PO8019 6,472,052 ART21US PO7980 6,356,715 ART22US PO80186,894,694 ART24US PO7938 6,636,216 ART25US PO8016 6,366,693 ART26USPO8024 6,329,990 ART27US PO7939 6,459,495 ART29US PO8501 6,137,500ART30US PO8500 6,690,416 ART31US PO7987 7,050,143 ART32US PO80226,398,328 ART33US PO8497 7,110,024 ART34US PO8020 6,431,704 ART38USPO8504 6,879,341 ART42US PO8000 6,415,054 ART43US PO7934 6,665,454ART45US PO7990 6,542,645 ART46US PO8499 6,486,886 ART47US PO85026,381,361 ART48US PO7981 6,317,192 ART50US PO7986 6,850,274 ART51USPO7983 09/113,054 ART52US PO8026 6,646,757 ART53US PO8028 6,624,848ART56US PO9394 6,357,135 ART57US PO9397 6,271,931 ART59US PO93986,353,772 ART60US PO9399 6,106,147 ART61US PO9400 6,665,008 ART62USPO9401 6,304,291 ART63US PO9403 6,305,770 ART65US PO9405 6,289,262ART66US PP0959 6,315,200 ART68US PP1397 6,217,165 ART69US PP23706,786,420 DOT01US PO8003 6,350,023 Fluid01US PO8005 6,318,849 Fluid02USPO8066 6,227,652 IJ01US PO8072 6,213,588 IJ02US PO8040 6,213,589 IJ03USPO8071 6,231,163 IJ04US PO8047 6,247,795 IJ05US PO8035 6,394,581 IJ06USPO8044 6,244,691 IJ07US PO8063 6,257,704 IJ08US PO8057 6,416,168 IJ09USPO8056 6,220,694 IJ10US PO8069 6,257,705 IJ11US PO8049 6,247,794 IJ12USPO8036 6,234,610 IJ13US PO8048 6,247,793 IJ14US PO8070 6,264,306 IJ15USPO8067 6,241,342 IJ16US PO8001 6,247,792 IJ17US PO8038 6,264,307 IJ18USPO8033 6,254,220 IJ19US PO8002 6,234,611 IJ20US PO8068 6,302,528 IJ21USPO8062 6,283,582 IJ22US PO8034 6,239,821 IJ23US PO8039 6,338,547 IJ24USPO8041 6,247,796 IJ25US PO8004 6,557,977 IJ26US PO8037 6,390,603 IJ27USPO8043 6,362,843 IJ28US PO8042 6,293,653 IJ29US PO8064 6,312,107 IJ30USPO9389 6,227,653 IJ31US PO9391 6,234,609 IJ32US PP0888 6,238,040 IJ33USPP0891 6,188,415 IJ34US PP0890 6,227,654 IJ35US PP0873 6,209,989 IJ36USPP0993 6,247,791 IJ37US PP0890 6,336,710 IJ38US PP1398 6,217,153 IJ39USPP2592 6,416,167 IJ40US PP2593 6,243,113 IJ41US PP3991 6,283,581 IJ42USPP3987 6,247,790 IJ43US PP3985 6,260,953 IJ44US PP3983 6,267,469 IJ45USPO7935 6,224,780 IJM01US PO7936 6,235,212 IJM02US PO7937 6,280,643IJM03US PO8061 6,284,147 IJM04US PO8054 6,214,244 IJM05US PO80656,071,750 IJM06US PO8055 6,267,905 IJM07US PO8053 6,251,298 IJM08USPO8078 6,258,285 IJM09US PO7933 6,225,138 IJM10US PO7950 6,241,904IJM11US PO7949 6,299,786 IJM12US PO8060 6,866,789 IJM13US PO80596,231,773 IJM14US PO8073 6,190,931 IJM15US PO8076 6,248,249 IJM16USPO8075 6,290,862 IJM17US PO8079 6,241,906 IJM18US PO8050 6,565,762IJM19US PO8052 6,241,905 IJM20US PO7948 6,451,216 IJM21US PO79516,231,772 IJM22US PO8074 6,274,056 IJM23US PO7941 6,290,861 IJM24USPO8077 6,248,248 IJM25US PO8058 6,306,671 IJM26US PO8051 6,331,258IJM27US PO8045 6,110,754 IJM28US PO7952 6,294,101 IJM29US PO80466,416,679 IJM30US PO9390 6,264,849 IJM31US PO9392 6,254,793 IJM32USPP0889 6,235,211 IJM35US PP0887 6,491,833 IJM36US PP0882 6,264,850IJM37US PP0874 6,258,284 IJM38US PP1396 6,312,615 IJM39US PP39896,228,668 IJM40US PP2591 6,180,427 IJM41US PP3990 6,171,875 IJM42USPP3986 6,267,904 IJM43US PP3984 6,245,247 IJM44US PP3982 6,315,914IJM45US PP0895 6,231,148 IR01US PP0869 6,293,658 IR04US PP0887 6,614,560IR05US PP0885 6,238,033 IR06US PP0884 6,312,070 IR10US PP0886 6,238,111IR12US PP0877 6,378,970 IR16US PP0878 6,196,739 IR17US PP0883 6,270,182IR19US PP0880 6,152,619 IR20US PO8006 6,087,638 MEMS02US PO80076,340,222 MEMS03US PO8010 6,041,600 MEMS05US PO8011 6,299,300 MEMS06USPO7947 6,067,797 MEMS07US PO7944 6,286,935 MEMS09US PO7946 6,044,646MEMS10US PP0894 6,382,769 MEMS13US

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the field of inkjet printing and, inparticular, discloses a method of manufacture of an ink jet printerhaving a thermal actuator comprising an external coil spring.

BACKGROUND OF THE INVENTION

Many ink jet printing mechanisms are known. Unfortunately, in massproduction techniques, the production of ink jet heads is quitedifficult. For example, often, the orifice or nozzle plate isconstructed separately from the ink supply and ink ejection mechanismand bonded to the mechanism at a later stage (Hewlett-Packard Journal,Vol. 36 no 5, pp 33-37 (1985)). These separate material processing stepsrequired in handling such precision devices often add a substantialexpense in manufacturing.

Additionally, side shooting ink jet technologies (U.S. Pat. No.4,899,181) are often used but again, this limits the amount of massproduction throughput given any particular capital investment.

Additionally, more esoteric techniques are also often utilized. Thesecan include electroforming of nickel stage (Hewlett-Packard Journal,Vol. 36 no 5, pp 33-37 (1985)), electro-discharge machining, laserablation (U.S. Pat. No. 5,208,604), micro-punching, etc.

The utilization of the above techniques is likely to add substantialexpense to the mass production of ink jet print heads and therefore addsubstantially to their final cost.

It would therefore be desirable if an efficient system for the massproduction of ink jet print heads could be developed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for a method ofmanufacture of an ink jet printer having a thermal actuator comprisingan external coil spring.

In accordance with a first aspect of the present invention, there isprovided a method of manufacture of an ink jet printer having a thermalactuator comprising an external coil spring wherein an array of nozzlesare formed on a substrate utilizing planar monolithic deposition,lithographic and etching processes.

Multiple ink jet heads are preferably formed simultaneously on a singleplanar substrate which can comprise a silicon wafer.

The print heads are preferably formed utilizing standard vlsi/ulsiprocessing with integrated drive electronics are preferably formed onthe same substrate. The integrated drive electronics may be formedutilizing a CMOS fabrication process.

Ink can be ejected from the substrate substantially normal to thesubstrate.

In accordance with a further aspect of the present invention, there isprovided a method of manufacture of a thermally actuated ink jet printercomprising a series of nozzle chambers which ejects ink via theutilization of a thermal actuator device, comprising the steps of: (a)initially providing a silicon wafer having a circuitry wafer layerincluding the electrical circuitry necessary for the operation of thethermal actuators on demand; (b) etching an ink inlet aperture in thecircuitry wafer layer; (c) depositing and etching a first sacrificiallayer on top of the silicon and circuitry wafer layer and etching thefirst sacrificial layer in an area defining a first portion of a nozzlechamber wall, a thermal actuator anchor and a thermal actuator endpoint; (d) depositing and etching a first inert material layer indefining a first actuator path starting at the thermal actuator anchor;(e) depositing and etching a first conductive material layer adjacentthe first actuator path and attached to the first inert material layer;(f) depositing and etching a non-conductive layer over the firstconductive material layer, the etching including etching predeterminedvias for interconnection of the first conductive material layer with asecond conductive material layer; (g) depositing and etching a secondinert material layer on top of the first inert material layer; (h)depositing and etching a second conductive material layer on top of thenon-conductive layer having a conductive interconnect to the firstconductive material layer; (i) depositing and etching a series of inertmaterial layers and sacrificial layers to form a nozzle chamberincluding an ink ejection hole and a nozzle chamber paddle attached toone of the inert material layers or the conductive layers at the thermalactuator end point; (j) etching an ink supply channel through the waferto the nozzle chamber; and (k) etching away the sacrificial layers.

The conductive material layers are preferably formed from a materialhaving a high Young's modulus such as titanium nitride. The first andsecond inert material layers can comprise substantially glass. The firstactuator path can comprise substantially a coil.

The steps are preferably also utilized to simultaneously separate thewafer into separate printheads.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 illustrates a single ink ejection mechanism as constructed inaccordance with the principles of the preferred embodiment;

FIG. 2 is a section through the line II-II of the actuator arm of FIG.1;

FIGS. 3-5 illustrate the basic operation of the ink ejection mechanismof the preferred embodiment;

FIG. 6 is an exploded perspective view of an ink ejection mechanism.

FIG. 7 provides a legend of the materials indicated in FIGS. 8 to 22;and

FIG. 8 to FIG. 22 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, there is provided an inkjet printer havinga series of ink ejection mechanisms wherein each ink ejection mechanismincludes a paddle actuated by a coil actuator, the coil spring actuatorhaving a unique cross section so as to provide for efficient actuationas a coiled thermal actuator.

Turning initially to FIG. 1, there is illustrated a single ink ejectionmechanism 1 constructed in accordance with the principles of thepreferred embodiment. The ink ejection mechanism 1 includes a chamber 2having a rim 3. The chamber 2 is normally filled with ink which bulgesout around a surface having a border along the edge of rim 3, the inkbeing retained within the chamber 2 by means of surface tension aroundthe rim 3. Outside of the chamber 2 is located a thermal actuator device5. The thermal actuator device 5 is interconnected via a strut 6 througha hole 7 to a paddle device within the chamber 2. The strut 6 and hole 7are treated so as to be hydrophobic. Further, the hole 7 is provided ina thin elongated form so that surface tension characteristics alsoassist in stopping any ink from flowing out of the hole 7.

The thermal actuator device 5 comprises a first arm portion 9 which canbe constructed from glass or other suitable non-conductive material. Asecond arm portion 10 can be constructed from material such as titaniumdiboride which has a large Young's modulus or bending strength andhence, when a current is passed through the titanium diboride layer 10,it expands with a predetermined coefficient of thermal expansion. Thethin strip 10 has a high Young's modulus or bending strength andtherefore the thin strip 10 is able to bend the much thicker strip 9which has a substantially lower Young's modulus.

Turning to FIG. 2, there is illustrated a cross-section of the armthrough the line II-II of FIG. 1 illustrating the structure of theactuator device 5. As described previously, the actuator device 5includes two titanium diboride portions 10 a, 10 b forming a circuitaround the coil in addition to the glass portion 9 which also providesfor electrical isolation of the two arms, the arms being conductivelyjoined at the strut end.

Turning now to FIGS. 3-5, there will now be explaining the operation ofthe ink ejection mechanism 1 for the ejection of ink. Initially, beforethe paddle 8 has started moving, the situation is as illustrated in FIG.3 with the nozzle chamber 2 being filled with ink and having a slightlybulging meniscus 12. Upon actuation of the actuator mechanism, thepaddle 8 begins to move towards the nozzle rim 3 resulting in asubstantial increase in pressure in the area around the nozzle rim 3.This in turn results in the situation as illustrated in FIG. 4 whereinthe meniscus begins to significantly bulge as a result of the increasesin pressure. Subsequently, the actuator is deactivated resulting in ageneral urge for the paddle 8 to return to its rest position. Thisresults in the ink being sucked back into the chamber 2 which in turnresults in the meniscus necking and breaking off into a meniscus 12 andink drop 14, the drop 14 proceeding to a paper or film medium (notshown) for marking. The meniscus 12 has generally a concave shape andsurface tension characteristics result in chamber refilling by means ofin flow 13 from an ink supply channel etched through the wafer. Therefilling is as a consequence of surface tension forces on the meniscus12. Eventually the meniscus returns to its quiescent state asillustrated in FIG. 3.

Turning now to FIG. 6, there is illustrated an exploded perspective viewof a single ink ejection mechanism 1 illustrating the various materiallayers. The ink ejection mechanism 1 can be formed as part of a largearray of mechanisms forming a print head with multiple print heads beingsimultaneously formed on a silicon wafer 17. The wafer 17 is initiallyprocessed so as to incorporate a standard CMOS circuitry layer 18 whichprovides for the electrical interconnect for the control of theconductive portions of the actuator. The CMOS layer 18 can be completedwith a silicon nitride passivation layer so as to protect it fromsubsequent processing steps in addition to ink flows through channel 20.The subsequent layers eg. 9, 10 and 2 can be deposited utilizingstandard micro-electro mechanical systems (MEMS) construction techniquesincluding the deposit of sacrificial aluminum layers in addition to thedeposit of the layers 10 constructed from titanium diboride the layer 9constructed from glass material and the nozzle chamber proper 2 againconstructed from titanium diboride. Each of these layers can be built upin a sacrificial material such as aluminum which is subsequently etchedaway. Further, an ink supply channel eg. 21 can be etched through thewafer 17. The etching can be by means of an isotropic crystallographicsilicon etch or an isotropic dry etch. A dry etch system capable of highaspect ratio silicon trench etching such as the Surface TechnologySystems (STS) Advance Silicon Etch (ASE) system is recommended.

Subsequent to construction of the nozzle arrangement 1, it can beattached to an ink supply apparatus for supplying ink to the reversesurface of the wafer 17 so that ink can flow into chamber 2.

The external surface of nozzle chamber 2 including rim 3, in addition tothe area surrounding slot 7, can then be hydrophobically treated so asto reduce the possibility of any ink exiting slot 7.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet print heads operating in accordance withthe principles taught by the present embodiment can proceed utilizingthe following steps:

-   1. Using a double sided polished wafer 17, Complete drive    transistors, data distribution, and timing circuits using a 0.5    micron, one poly, 2 metal CMOS process to form layer 18. This step    is shown in FIG. 8. For clarity, these diagrams may not be to scale,    and may not represent a cross section though any single plane of the    nozzle. FIG. 7 is a key to representations of various materials in    these manufacturing diagrams, and those of other cross referenced    ink jet configurations.-   2. Etch oxide layer 18 down to silicon or aluminum using Mask 1.    This mask defines the ink inlet, the heater contact vias, and the    edges of the print heads chip. This step is shown in FIG. 9.-   3. Deposit 1 micron of sacrificial material 30 (e.g. aluminum).-   4. Etch the sacrificial layer 30 using Mask 2, defining the nozzle    chamber wall and the actuator anchor point. This step is shown in    FIG. 10.-   5. Deposit 1 micron of glass 31.-   6. Etch the glass 31 using Mask 3, which defines the lower layer of    the actuator loop.-   7. Deposit 1 micron of heater material 32, for example titanium    nitride (TiN) or titanium diboride (TiB₂). Planarize using CMP.    Steps 5 to 7 form a ‘damascene’ process. This step is shown in FIG.    11.-   8. Deposit 0.1 micron of silicon nitride (not shown).-   9. Deposit 1 micron of glass 33.-   10. Etch the glass 33 using Mask 4, which defines the upper layer of    the actuator loop.-   11. Etch the silicon nitride using Mask 5, which defines the vias    connecting the upper layer of the actuator loop to the lower layer    of the actuator loop.-   12. Deposit 1 micron of the same heater material 34 as in step 7    heater material 32. Planarize using CMP. Steps 8 to 12 form a ‘dual    damascene’ process. This step is shown in FIG. 12.-   13. Etch the glass down to the sacrificial layer 30 using Mask 6,    which defines the actuator and the nozzle chamber wall, with the    exception of the nozzle chamber actuator slot. This step is shown in    FIG. 13.-   14. Wafer probe. All electrical connections are complete at this    point, bond pads are accessible, and the chips are not yet    separated.-   15. Deposit 3 microns of sacrificial material 35.-   16. Etch the sacrificial layer 35 down to glass using Mask 7, which    defines the nozzle chamber wall, with the exception of the nozzle    chamber actuator slot. This step is shown in FIG. 14.-   17. Deposit 1 micron of PECVD glass 36 and planarize down to the    sacrificial layer 35 using CMP. This step is shown in FIG. 15.-   18. Deposit 5 microns of sacrificial material 37.-   19. Etch the sacrificial material 37 down to glass using Mask 8.    This mask defines the nozzle chamber wall and the paddle. This step    is shown in FIG. 16.-   20. Deposit 3 microns of PECVD glass 38 and planarize down to the    sacrificial layer 37 using CMP.-   21. Deposit 1 micron of sacrificial material 39.-   22. Etch the sacrificial material 39 down to glass using Mask 9.    This mask defines the nozzle chamber wall. This step is shown in    FIG. 17.-   23. Deposit 3 microns of PECVD glass 40.-   24. Etch to a depth of (approx.) 1 micron using Mask 10. This mask    defines the nozzle rim 3. This step is shown in FIG. 18.-   25. Etch down to the sacrificial layer 39 using Mask 11. This mask    defines the roof of the nozzle chamber, and the nozzle itself. This    step is shown in FIG. 19.-   26. Back-etch completely through the silicon wafer (with, for    example, an ASE Advanced Silicon Etcher from Surface Technology    Systems) using Mask 12. This mask defines the ink inlets 21 which    are etched through the wafer. The wafer is also diced by this etch.    This step is shown in FIG. 20.-   27. Etch the sacrificial material 30, 35, 37, 39. The nozzle    chambers are cleared, the actuators freed, and the chips are    separated by this etch. This step is shown in FIG. 21.-   28. Mount the print heads in their packaging, which may be a molded    plastic former incorporating ink channels which supply the    appropriate color ink to the ink inlets at the back of the wafer.-   29. Connect the print heads to their interconnect systems. For a low    profile connection with minimum disruption of airflow, TAB may be    used. Wire bonding may also be used if the printer is to be operated    with sufficient clearance to the paper.-   30. Hydrophobize the front surface of the print heads.-   31. Fill the completed print heads with ink 41 and test them. A    filled nozzle is shown in FIG. 22.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing system including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters high speed pagewidth printers, notebook computers with in-builtpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic“minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per print head, but is a majorimpediment to the fabrication of pagewidth print heads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table above under the heading CrossReferences to Related Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems

For ease of manufacture using standard process equipment, the print headis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the print head is 100mm long, with a width which depends upon the ink jet type. The smallestprint head designed is IJ38, which is 0.35 mm wide, giving a chip areaof 35 square mm. The print heads each contain 19,200 nozzles plus dataand control circuitry.

Ink is supplied to the back of the print head by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprint head is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 which matches the docket numbers in the in the table under theheading Cross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet print heads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, a printer may be listed more than once in a table, where itshares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) DescriptionAdvantages Disadvantages Examples Thermal An electrothermal Large forceHigh power Canon Bubblejet bubble heater heats the ink to generated Inkcarrier limited to 1979 Endo et al GB above boiling point, Simpleconstruction water patent 2,007,162 transferring significant No movingparts Low efficiency Xerox heater-in-pit heat to the aqueous Fastoperation High temperatures 1990 Hawkins et al ink. A bubble Small chiparea required U.S. Pat. No. 4,899,181 nucleates and quickly required foractuator High mechanical Hewlett-Packard TIJ forms, expelling the stress1982 Vaught et al ink. Unusual materials U.S. Pat. No. 4,490,728 Theefficiency of the required process is low, with Large drive typicallyless than transistors 0.05% of the electrical Cavitation causes energybeing actuator failure transformed into Kogation reduces kinetic energyof the bubble formation drop. Large print heads are difficult tofabricate Piezoelectric A piezoelectric crystal Low power Very largearea Kyser et al U.S. Pat. No. such as lead consumption required foractuator 3,946,398 lanthanum zirconate Many ink types can Difficult tointegrate Zoltan U.S. Pat. No. (PZT) is electrically be used withelectronics 3,683,212 activated, and either Fast operation High voltagedrive 1973 Stemme U.S. Pat. No. expands, shears, or High efficiencytransistors required 3,747,120 bends to apply Full pagewidth print EpsonStylus pressure to the ink, heads impractical Tektronix ejecting drops.due to actuator size IJ04 Requires electrical poling in high fieldstrengths during manufacture Electro- An electric field is Low power Lowmaximum Seiko Epson, Usui strictive used to activate consumption strain(approx. et all JP 253401/96 electrostriction in Many ink types can0.01%) IJ04 relaxor materials such be used Large area required as leadlanthanum Low thermal for actuator due to zirconate titanate expansionlow strain (PLZT) or lead Electric field Response speed is magnesiumniobate strength required marginal (~10 μs) (PMN). (approx. 3.5 V/μm)High voltage drive can be generated transistors required withoutdifficulty Full pagewidth print Does not require heads impracticalelectrical poling due to actuator size Ferroelectric An electric fieldis Low power Difficult to integrate IJ04 used to induce a phaseconsumption with electronics transition between the Many ink types canUnusual materials antiferroelectric (AFE) be used such as PLZSnT are andferroelectric (FE) Fast operation required phase. Perovskite (<1 μs)Actuators require a materials such as tin Relatively high large areamodified lead longitudinal strain lanthanum zirconate High efficiencytitanate (PLZSnT) Electric field exhibit large strains of strength ofaround 3 V/μm up to 1% associated can be readily with the AFE to FEprovided phase transition. Electrostatic Conductive plates are Low powerDifficult to operate IJ02, IJ04 plates separated by a consumptionelectrostatic devices compressible or fluid Many ink types can in anaqueous dielectric (usually air). be used environment Upon applicationof a Fast operation The electrostatic voltage, the plates actuator willattract each other and normally need to be displace ink, causingseparated from the drop ejection. The ink conductive plates may Verylarge area be in a comb or required to achieve honeycomb structure, highforces or stacked to increase High voltage drive the surface area andtransistors may be therefore the force. required Full pagewidth printheads are not competitive due to actuator size Electrostatic A strongelectric field Low current High voltage 1989 Saito et al, pull isapplied to the ink, consumption required U.S. Pat. No. 4,799,068 on inkwhereupon Low temperature May be damaged by 1989 Miura et al,electrostatic attraction sparks due to air U.S. Pat. No. 4,810,954accelerates the ink breakdown Tone-jet towards the print Required fieldmedium. strength increases as the drop size decreases High voltage drivetransistors required Electrostatic field attracts dust Permanent Anelectromagnet Low power Complex fabrication IJ07, IJ10 magnet directlyattracts a consumption Permanent magnetic electro- permanent magnet,Many ink types can material such as magnetic displacing ink and be usedNeodymium Iron causing drop ejection. Fast operation Boron (NdFeB) Rareearth magnets High efficiency required. with a field strength Easyextension from High local currents around 1 Tesla can be single nozzlesto required used. Examples are: pagewidth print Copper metalizationSamarium Cobalt heads should be used for (SaCo) and magnetic longmaterials in the electromigration neodymium iron boron lifetime and lowfamily (NdFeB, resistivity NdDyFeBNb, Pigmented inks are NdDyFeB, etc)usually infeasible Operating temperature limited to the Curietemperature (around 540 K) Soft A solenoid induced a Low power Complexfabrication IJ01, IJ05, IJ08, magnetic magnetic field in a softconsumption Materials not IJ10, IJ12, IJ14, core magnetic core or yokeMany ink types can usually present in a IJ15, IJ17 electro- fabricatedfrom a be used CMOS fab such as magnetic ferrous material such Fastoperation NiFe, CoNiFe, or as electroplated iron High efficiency CoFeare required alloys such as CoNiFe Easy extension from High localcurrents [1], CoFe, or NiFe single nozzles to required alloys.Typically, the pagewidth print Copper metalization soft magneticmaterial heads should be used for is in two parts, which long arenormally held electromigration apart by a spring. lifetime and low Whenthe solenoid is resistivity actuated, the two parts Electroplating isattract, displacing the required ink. High saturation flux density isrequired (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz The Lorenzforce Low power Force acts as a IJ06, IJ11, IJ13, force acting on acurrent consumption twisting motion IJ16 carrying wire in a Many inktypes can Typically, only a magnetic field is be used quarter of theutilized. Fast operation solenoid length This allows the High efficiencyprovides force in a magnetic field to be Easy extension from usefuldirection supplied externally to single nozzles to High local currentsthe print head, for pagewidth print required example with rare headsCopper metalization earth permanent should be used for magnets. longOnly the current electromigration carrying wire need be lifetime and lowfabricated on the print- resistivity head, simplifying Pigmented inksare materials usually infeasible requirements. Magneto- The actuatoruses the Many ink types can Force acts as a Fischenbeck, U.S. Pat. No.striction giant magnetostrictive be used twisting motion 4,032,929effect of materials Fast operation Unusual materials IJ25 such asTerfenol-D (an Easy extension from such as Terfenol-D alloy of terbium,single nozzles to are required dysprosium and iron pagewidth print Highlocal currents developed at the Naval heads required OrdnanceLaboratory, High force is Copper metalization hence Ter-Fe-NOL).available should be used for For best efficiency, the long actuatorshould be pre- electromigration stressed to approx. 8 MPa. lifetime andlow resistivity Pre-stressing may be required Surface Ink under positiveLow power Requires Silverbrook, EP tension pressure is held in aconsumption supplementary force 0771 658 A2 and reduction nozzle bysurface Simple construction to effect drop related patent tension. Thesurface No unusual separation applications tension of the ink ismaterials required in Requires special ink reduced below the fabricationsurfactants bubble threshold, High efficiency Speed may be causing theink to Easy extension from limited by surfactant egress from the singlenozzles to properties nozzle. pagewidth print heads Viscosity The inkviscosity is Simple construction Requires Silverbrook, EP reductionlocally reduced to No unusual supplementary force 0771 658 A2 and selectwhich drops are materials required in to effect drop related patent tobe ejected. A fabrication separation applications viscosity reductioncan Easy extension from Requires special ink be achieved single nozzlesto viscosity properties electrothermally with pagewidth print High speedis most inks, but special heads difficult to achieve inks can beengineered Requires oscillating for a 100:1 viscosity ink pressurereduction. A high temperature difference (typically 80 degrees) isrequired Acoustic An acoustic wave is Can operate without Complex drive1993 Hadimioglu et generated and a nozzle plate circuitry al, EUP550,192 focussed upon the Complex fabrication 1993 Elrod et al, dropejection region. Low efficiency EUP 572,220 Poor control of dropposition Poor control of drop volume Thermo- An actuator which Low powerEfficient aqueous IJ03, IJ09, IJ17, elastic relies upon differentialconsumption operation requires a IJ18, IJ19, IJ20, bend thermalexpansion Many ink types can thermal insulator on IJ21, IJ22, IJ23,actuator upon Joule heating is be used the hot side IJ24, IJ27, IJ28,used. Simple planar Corrosion IJ29, IJ30, IJ31, fabrication preventioncan be IJ32, IJ33, IJ34, Small chip area difficult IJ35, IJ36, IJ37,required for each Pigmented inks may IJ38, IJ39, IJ40, actuator beinfeasible, as IJ41 Fast operation pigment particles High efficiency mayjam the bend CMOS compatible actuator voltages and currents StandardMEMS processes can be used Easy extension from single nozzles topagewidth print heads High CTE A material with a very High force can beRequires special IJ09, IJ17, IJ18, thermo- high coefficient of generatedmaterial (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermal expansion Threemethods of Requires a PTFE IJ23, IJ24, IJ27, actuator (CTE) such as PTFEdeposition are deposition process, IJ28, IJ29, IJ30,polytetrafluoroethylene under development: which is not yet IJ31, IJ42,IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTEmaterials deposition (CVD), fabs are usually non- spin coating, and PTFEdeposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a candidate with high conductive material isfor low dielectric temperature (above incorporated. A 50 μm constantinsulation 350° C.) processing long PTFE bend in ULSI Pigmented inks mayactuator with Very low power be infeasible, as polysilicon heater andconsumption pigment particles 15 mW power input Many ink types can mayjam the bend can provide 180 μN be used actuator force and 10 μm Simpleplanar deflection. Actuator fabrication motions include: Small chip areaBend required for each Push actuator Buckle Fast operation Rotate Highefficiency CMOS compatible voltages and currents Easy extension fromsingle nozzles to pagewidth print heads Conductive A polymer with a highHigh force can be Requires special IJ24 polymer coefficient of thermalgenerated materials thermo- expansion (such as Very low powerdevelopment (High elastic PTFE) is doped with consumption CTE conductiveactuator conducting substances Many ink types can polymer) to increaseits be used Requires a PTFE conductivity to about 3 Simple planardeposition process, orders of magnitude fabrication which is not yetbelow that of copper. Small chip area standard in ULSI The conductingrequired for each fabs polymer expands actuator PTFE deposition whenresistively Fast operation cannot be followed heated. High efficiencywith high Examples of CMOS compatible temperature (above conductingdopants voltages and 350° C.) processing include: currents Evaporationand Carbon nanotubes Easy extension from CVD deposition Metal fiberssingle nozzles to techniques cannot Conductive polymers pagewidth printbe used such as doped heads Pigmented inks may polythiophene beinfeasible, as Carbon granules pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) is developed at the Naval available (more thanrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate limited between its weakresistance by heat removal martensitic state and Simple constructionRequires unusual its high stiffness Easy extension from materials (TiNi)austenic state. The single nozzles to The latent heat of shape of theactuator pagewidth print transformation must in its martensitic stateheads be provided is deformed relative to Low voltage High current theaustenic shape. operation operation The shape change Requires pre-causes ejection of a stressing to distort drop. the martensitic stateLinear Linear magnetic Linear Magnetic Requires unusual IJ12 Magneticactuators include the actuators can be semiconductor Actuator LinearInduction constructed with materials such as Actuator (LIA), Linear highthrust, long soft magnetic alloys Permanent Magnet travel, and high(e.g. CoNiFe) Synchronous Actuator efficiency using Some varieties also(LPMSA), Linear planar require permanent Reluctance semiconductormagnetic materials Synchronous Actuator fabrication such as Neodymium(LRSA), Linear techniques iron boron (NdFeB) Switched Reluctance Longactuator travel Requires complex Actuator (LSRA), and is availablemulti-phase drive the Linear Stepper Medium force is circuitry Actuator(LSA). available High current Low voltage operation operation

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesActuator This is the simplest Simple operation Drop repetition rateThermal ink jet directly mode of operation: the No external fields isusually limited to Piezoelectric ink jet pushes ink actuator directlyrequired around 10 kHz. IJ01, IJ02, IJ03, supplies sufficient Satellitedrops can However, this is not IJ04, IJ05, IJ06, kinetic energy to expelbe avoided if drop fundamental to the IJ07, IJ09, IJ11, the drop. Thedrop velocity is less than method, but is IJ12, IJ14, IJ16, must have asufficient 4 m/s related to the refill IJ20, IJ22, IJ23, velocity toovercome Can be efficient, method normally IJ24, IJ25, IJ26, the surfacetension. depending upon the used IJ27, IJ28, IJ29, actuator used All ofthe drop IJ30, IJ31, IJ32, kinetic energy must IJ33, IJ34, IJ35, beprovided by the IJ36, IJ37, IJ38, actuator IJ39, IJ40, IJ41, Satellitedrops IJ42, IJ43, IJ44 usually form if drop velocity is greater than 4.5m/s Proximity The drops to be Very simple print Requires closeSilverbrook, EP printed are selected by head fabrication can proximitybetween 0771 658 A2 and some manner (e.g. be used the print head andrelated patent thermally induced The drop selection the print media orapplications surface tension means does not need transfer rollerreduction of to provide the May require two pressurized ink). energyrequired to print heads printing Selected drops are separate the dropalternate rows of the separated from the ink from the nozzle image inthe nozzle by Monolithic color contact with the print print heads aremedium or a transfer difficult roller. Electrostatic The drops to beVery simple print Requires very high Silverbrook, EP pull printed areselected by head fabrication can electrostatic field 0771 658 A2 and onink some manner (e.g. be used Electrostatic field related patentthermally induced The drop selection for small nozzle applicationssurface tension means does not need sizes is above air Tone-Jetreduction of to provide the breakdown pressurized ink). energy requiredto Electrostatic field Selected drops are separate the drop may attractdust separated from the ink from the nozzle in the nozzle by a strongelectric field. Magnetic The drops to be Very simple print Requiresmagnetic Silverbrook, EP pull on ink printed are selected by headfabrication can ink 0771 658 A2 and some manner (e.g. be used Ink colorsother than related patent thermally induced The drop selection black aredifficult applications surface tension means does not need Requires veryhigh reduction of to provide the magnetic fields pressurized ink).energy required to Selected drops are separate the drop separated fromthe ink from the nozzle in the nozzle by a strong magnetic field actingon the magnetic ink. Shutter The actuator moves a High speed (>50 kHz)Moving parts are IJ13, IJ17, IJ21 shutter to block ink operation canrequired flow to the nozzle. The be achieved due to Requires ink inkpressure is pulsed reduced refill time pressure modulator at a multipleof the Drop timing can be Friction and wear drop ejection very accuratemust be considered frequency. The actuator energy Stiction is possiblecan be very low Shuttered The actuator moves a Actuators with Movingparts are IJ08, IJ15, IJ18, grill shutter to block ink small travel canbe required IJ19 flow through a grill to used Requires ink the nozzle.The shutter Actuators with pressure modulator movement need only smallforce can be Friction and wear be equal to the width used must beconsidered of the grill holes. High speed (>50 kHz) Stiction is possibleoperation can be achieved Pulsed A pulsed magnetic Extremely lowRequires an external IJ10 magnetic field attracts an ‘ink energyoperation is pulsed magnetic pull on ink pusher’ at the drop possiblefield pusher ejection frequency. An No heat dissipation Requires specialactuator controls a problems materials for both catch, which preventsthe actuator and the the ink pusher from ink pusher moving when a dropis Complex not to be ejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator directly Simplicity of Dropejection Most ink jets, fires the ink drop, and construction energy mustbe including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical size actuator IJ01, IJ02,IJ03, IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP inkoscillates, providing pressure can provide ink pressure 0771 658 A2 andpressure much of the drop a refill pulse, oscillator related patent(including ejection energy. The allowing higher Ink pressure phaseapplications acoustic actuator selects which operating speed andamplitude must IJ08, IJ13, IJ15, stimulation) drops are to be fired Theactuators may be carefully IJ17, IJ18, IJ19, by selectively operate withmuch controlled IJ21 blocking or enabling lower energy Acousticreflections nozzles. The ink Acoustic lenses can in the ink chamberpressure oscillation be used to focus the must be designed may beachieved by sound on the for vibrating the print nozzles head, orpreferably by an actuator in the ink supply. Media The print head is Lowpower Precision assembly Silverbrook, EP proximity placed in close Highaccuracy required 0771 658 A2 and proximity to the print Simple printhead Paper fibers may related patent medium. Selected construction causeproblems applications drops protrude from Cannot print on the print headfurther rough substrates than unselected drops, and contact the printmedium. The drop soaks into the medium fast enough to cause dropseparation. Transfer Drops are printed to a High accuracy BulkySilverbrook, EP roller transfer roller instead Wide range of printExpensive 0771 658 A2 and of straight to the print substrates can beComplex related patent medium. A transfer used construction applicationsroller can also be used Ink can be dried on Tektronix hot melt forproximity drop the transfer roller piezoelectric ink jet separation. Anyof the IJ series Electrostatic An electric field is Low power Fieldstrength Silverbrook, EP used to accelerate Simple print head requiredfor 0771 658 A2 and selected drops towards construction separation ofsmall related patent the print medium. drops is near or applicationsabove air Tone-Jet breakdown Direct A magnetic field is Low powerRequires magnetic Silverbrook, EP magnetic used to accelerate Simpleprint head ink 0771 658 A2 and field selected drops of constructionRequires strong related patent magnetic ink towards magnetic fieldapplications the print medium. Cross The print head is Does not requireRequires external IJ06, IJ16 magnetic placed in a constant magneticmaterials magnet field magnetic field. The to be integrated in Currentdensities Lorenz force in a the print head may be high, current carryingwire manufacturing resulting in is used to move the processelectromigration actuator. problems Pulsed A pulsed magnetic Very lowpower Complex print head IJ10 magnetic field is used to operation ispossible construction field cyclically attract a Small print headMagnetic materials paddle, which pushes size required in print on theink. A small head actuator moves a catch, which selectively prevents thepaddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many actuatorThermal Bubble Ink mechanical simplicity mechanisms have jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be taken IJ18, IJ19, IJ20, actuator The expansion may be thatthe materials do IJ21, IJ22, IJ23, thermal, piezoelectric, notdelaminate IJ24, IJ27, IJ29, magnetostrictive, or Residual bend IJ30,IJ31, IJ32, other mechanism. The resulting from high IJ33, IJ34, IJ35,bend actuator converts temperature or high IJ36, IJ37, IJ38, a highforce low travel stress during IJ39, IJ42, IJ43, actuator mechanism toformation IJ44 high travel, lower force mechanism. Transient A trilayerbend Very good High stresses are IJ40, IJ41 bend actuator where the twotemperature stability involved actuator outside layers are High speed,as a Care must be taken identical. This cancels new drop can be that thematerials do bend due to ambient fired before heat not delaminatetemperature and dissipates residual stress. The Cancels residualactuator only responds stress of formation to transient heating of oneside or the other. Reverse The actuator loads a Better coupling toFabrication IJ05, IJ11 spring spring. When the the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some piezoelectricstack actuators are stacked. Reduced drive fabrication ink jets This canbe voltage complexity IJ04 appropriate where Increased possibilityactuators require high of short circuits due electric field strength, topinholes such as electrostatic and piezoelectric actuators. MultipleMultiple smaller Increases the force Actuator forces may IJ12, IJ13,IJ18, actuators actuators are used available from an not add linearly,IJ20, IJ22, IJ28, simultaneously to actuator reducing efficiency IJ42,IJ43 move the ink. Each Multiple actuators actuator need provide can bepositioned to only a portion of the control ink flow force required.accurately Linear A linear spring is used Matches low travel Requiresprint head IJ15 Spring to transform a motion actuator with higher areafor the spring with small travel and travel requirements high force intoa Non-contact method longer travel, lower of motion force motion.transformation Coiled A bend actuator is Increases travel Generallyrestricted IJ17, IJ21, IJ34, actuator coiled to provide Reduces chiparea to planar IJ35 greater travel in a Planar implementations reducedchip area. implementations are due to extreme relatively easy tofabrication difficulty fabricate. in other orientations. Flexure A bendactuator has a Simple means of Care must be taken IJ10, IJ19, IJ33 bendsmall region near the increasing travel of not to exceed the actuatorfixture point, which a bend actuator elastic limit in the flexes muchmore flexure area readily than the Stress distribution is remainder ofthe very uneven actuator. The actuator Difficult to flexing iseffectively accurately model converted from an with finite element evencoiling to an analysis angular bend, resulting in greater travel of theactuator tip. Catch The actuator controls a Very low actuator ComplexIJ10 small catch. The catch energy construction either enables or Verysmall actuator Requires external disables movement of size force an inkpusher that is Unsuitable for controlled in a bulk pigmented inksmanner. Gears Gears can be used to Low force, low Moving parts are IJ13increase travel at the travel actuators can required expense ofduration. be used Several actuator Circular gears, rack Can befabricated cycles are required and pinion, ratchets, using standard Morecomplex drive and other gearing surface MEMS electronics methods can beused. processes Complex construction Friction, friction, and wear arepossible Buckle A buckle plate can be Very fast movement Must staywithin S. Hirata et al, “An plate used to change a slow achievableelastic limits of the Ink-jet Head Using actuator into a fast materialsfor long Diaphragm motion. It can also device life Microactuator”,convert a high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved February 1996, pp 418-423. into a high travel, Generally highIJ18, IJ27 medium force motion. power requirement Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low travel High stress around IJ32,IJ36, IJ37 used to transform a actuator with higher the fulcrum motionwith small travel requirements travel and high force Fulcrum area has nointo a motion with linear movement, longer travel and and can be usedfor lower force. The lever a fluid seal can also reverse the directionof travel. Rotary The actuator is High mechanical Complex IJ28 impellerconnected to a rotary advantage construction impeller. A small The ratioof force to Unsuitable for angular deflection of travel of the actuatorpigmented inks the actuator results in can be matched to a rotation ofthe the nozzle impeller vanes, which requirements by push the inkagainst varying the number stationary vanes and of impeller vanes out ofthe nozzle. Acoustic A refractive or No moving parts Large area required1993 Hadimioglu et lens diffractive (e.g. zone Only relevant for al, EUP550,192 plate) acoustic lens is acoustic ink jets 1993 Elrod et al, usedto concentrate EUP 572,220 sound waves. Sharp A sharp point is usedSimple construction Difficult to fabricate Tone-jet conductive toconcentrate an using standard VLSI point electrostatic field. processesfor a surface ejecting ink- jet Only relevant for electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the Simple construction High energy is Hewlett-Packardexpansion actuator changes, in the case of typically required to ThermalInk jet pushing the ink in all thermal ink jet achieve volume CanonBubblejet directions. expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator moves in Efficient coupling to High fabrication IJ01, IJ02,IJ04, normal to a direction normal to ink drops ejected complexity maybe IJ07, IJ11, IJ14 chip the print head surface. normal to the requiredto achieve surface The nozzle is typically surface perpendicular in theline of motion movement. Parallel to The actuator moves Suitable forplanar Fabrication IJ12, IJ13, IJ15, chip parallel to the printfabrication complexity IJ33, , IJ34, IJ35, surface head surface. DropFriction IJ36 ejection may still be Stiction normal to the surface.Membrane An actuator with a The effective area of Fabrication 1982Howkins U.S. Pat. No. push high force but small the actuator complexity4,459,601 area is used to push a becomes the Actuator size stiffmembrane that is membrane area Difficulty of in contact with the ink.integration in a VLSI process Rotary The actuator causes Rotary leversmay Device complexity IJ05, IJ08, IJ13, the rotation of some be used toincrease May have friction at IJ28 element, such a grill or travel apivot point impeller Small chip area requirements Bend The actuatorbends A very small change Requires the 1970 Kyser et al when energized.This in dimensions can actuator to be made U.S. Pat. No. 3,946,398 maybe due to be converted to a from at least two 1973 Stemme U.S. Pat. No.differential thermal large motion. distinct layers, or to 3,747,120expansion, have a thermal IJ03, IJ09, IJ10, piezoelectric differenceacross the IJ19, IJ23, IJ24, expansion, actuator IJ25, IJ29, IJ30,magnetostriction, or IJ31, IJ33, IJ34, other form of relative IJ35dimensional change. Swivel The actuator swivels Allows operationInefficient coupling IJ06 around a central pivot. where the net linearto the ink motion This motion is suitable force on the paddle wherethere are is zero opposite forces Small chip area applied to oppositerequirements sides of the paddle, e.g. Lorenz force. Straighten Theactuator is Can be used with Requires careful IJ26, IJ32 normally bent,and shape memory balance of stresses straightens when alloys where theto ensure that the energized. austenic phase is quiescent bend is planaraccurate Double The actuator bends in One actuator can be Difficult tomake IJ36, IJ37, IJ38 bend one direction when used to power two thedrops ejected by one element is nozzles. both bend directions energized,and bends Reduced chip size. identical. the other way when Not sensitiveto A small efficiency another element is ambient temperature losscompared to energized. equivalent single bend actuators. ShearEnergizing the Can increase the Not readily 1985 Fishbeck U.S. Pat. No.actuator causes a shear effective travel of applicable to other4,584,590 motion in the actuator piezoelectric actuator material.actuators mechanisms Radial The actuator squeezes Relatively easy toHigh force required 1970 Zoltan U.S. Pat. No. constriction an inkreservoir, fabricate single Inefficient 3,683,212 forcing ink from anozzles from glass Difficult to integrate constricted nozzle. tubing aswith VLSI macroscopic processes structures Coil/ A coiled actuator Easyto fabricate as Difficult to fabricate IJ17, IJ21, IJ34, uncoil uncoilsor coils more a planar VLSI for non-planar IJ35 tightly. The motion ofprocess devices the free end of the Small area required, Poorout-of-plane actuator ejects the ink. therefore low cost stiffness BowThe actuator bows (or Can increase the Maximum travel is IJ16, IJ18,IJ27 buckles) in the middle speed of travel constrained when energized.Mechanically rigid High force required Push-Pull Two actuators controlThe structure is Not readily suitable IJ18 a shutter. One actuatorpinned at both ends, for ink jets which pulls the shutter, and so has ahigh out-of- directly push the ink the other pushes it. plane rigidityCurl A set of actuators curl Good fluid flow to Design complexity IJ20,IJ42 inwards inwards to reduce the the region behind volume of ink thatthe actuator they enclose. increases efficiency Curl A set of actuatorscurl Relatively simple Relatively large IJ43 outwards outwards,pressurizing construction chip area ink in a chamber surrounding theactuators, and expelling ink from a nozzle in the chamber. Iris Multiplevanes enclose High efficiency High fabrication IJ22 a volume of ink.These Small chip area complexity simultaneously rotate, Not suitable forreducing the volume pigmented inks between the vanes. Acoustic Theactuator vibrates The actuator can be Large area required 1993Hadimioglu et vibration at a high frequency. physically distant forefficient al, EUP 550,192 from the ink operation at useful 1993 Elrod etal, frequencies EUP 572,220 Acoustic coupling and crosstalk Complexdrive circuitry Poor control of drop volume and position None In variousink jet No moving parts Various other Silverbrook, EP designs theactuator tradeoffs are 0771 658 A2 and does not move. required torelated patent eliminate moving applications parts Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way Fabrication Low speed Thermal ink jettension that ink jets are simplicity Surface tension Piezoelectric inkjet refilled. After the Operational force relatively IJ01-IJ07,IJ10-IJ14, actuator is energized, simplicity small compared to IJ16,IJ20, IJ22-IJ45 it typically returns actuator force rapidly to itsnormal Long refill time position. This rapid usually dominates returnsucks in air the total repetition through the nozzle rate opening. Theink surface tension at the nozzle then exerts a small force restoringthe meniscus to a minimum area. This force refills the nozzle. ShutteredInk to the nozzle High speed Requires common IJ08, IJ13, IJ15,oscillating chamber is provided at Low actuator ink pressure IJ17, IJ18,IJ19, ink a pressure that energy, as the oscillator IJ21 pressureoscillates at twice the actuator need only May not be suitable dropejection open or close the for pigmented inks frequency. When a shutter,instead of drop is to be ejected, ejecting the ink drop the shutter isopened for 3 half cycles: drop ejection, actuator return, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main High speed, asthe Requires two IJ09 actuator actuator has ejected a nozzle is activelyindependent drop a second (refill) refilled actuators per nozzleactuator is energized. The refill actuator pushes ink into the nozzlechamber. The refill actuator returns slowly, to prevent its return fromemptying the chamber again. Positive The ink is held a slight Highrefill rate, Surface spill must Silverbrook, EP ink positive pressure.therefore a high be prevented 0771 658 A2 and pressure After the inkdrop is drop repetition rate Highly hydrophobic related patent ejected,the nozzle is possible print head surfaces applications chamber fillsquickly are required Alternative for:, as surface tension and IJ01-IJ07,IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate to refill thenozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel Designsimplicity Restricts refill rate Thermal ink jet channel to the nozzlechamber Operational May result in a Piezoelectric ink jet is made longand simplicity relatively large chip IJ42, IJ43 relatively narrow,Reduces crosstalk area relying on viscous Only partially drag to reduceinlet effective back-flow. Positive The ink is under a Drop selectionand Requires a method Silverbrook, EP ink positive pressure, soseparation forces (such as a nozzle 0771 658 A2 and pressure that in thequiescent can be reduced rim or effective related patent state some ofthe ink Fast refill time hydrophobizing, or applications drop alreadyprotrudes both) to prevent Possible operation from the nozzle. floodingof the of the following: This reduces the ejection surface of IJ01-IJ07,IJ09-IJ12, pressure in the nozzle the print head. IJ14, IJ16, chamberwhich is IJ20, IJ22, IJ23-IJ34, required to eject a IJ36-IJ41, certainvolume of ink. IJ44 The reduction in chamber pressure results in areduction in ink pushed out through the inlet. Baffle One or morebaffles The refill rate is not Design complexity HP Thermal Ink Jet areplaced in the inlet as restricted as the May increase Tektronix inkflow. When the long inlet method. fabrication piezoelectric ink jetactuator is energized, Reduces crosstalk complexity (e.g. the rapid inkTektronix hot melt movement creates Piezoelectric print eddies whichrestrict heads). the flow through the inlet. The slower refill processis unrestricted, and does not result in eddies. Flexible In this methodrecently Significantly Not applicable to Canon flap disclosed by Canon,reduces back-flow most ink jet restricts the expanding actuator foredge-shooter configurations inlet (bubble) pushes on a thermal ink jetIncreased flexible flap that devices fabrication restricts the inlet.complexity Inelastic deformation of polymer flap results in creep overextended use Inlet filter A filter is located Additional Restrictsrefill rate IJ04, IJ12, IJ24, between the ink inlet advantage of ink Mayresult in IJ27, IJ29, IJ30 and the nozzle filtration complex chamber.The filter Ink filter may be construction has a multitude of fabricatedwith no small holes or slots, additional process restricting ink flow.steps The filter also removes particles which may block the nozzle.Small inlet The ink inlet channel Design simplicity Restricts refillrate IJ02, IJ37, IJ44 compared to the nozzle chamber May result in a tonozzle has a substantially relatively large chip smaller cross sectionarea than that of the nozzle, Only partially resulting in easier inkeffective egress out of the nozzle than out of the inlet. Inlet Asecondary actuator Increases speed of Requires separate IJ09 shuttercontrols the position of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowproblem Requires careful IJ01, IJ03, IJ05, located problem of inletback- is eliminated design to minimize IJ06, IJ07, IJ10, behind the flowby arranging the the negative IJ11, IJ14, IJ16, ink- ink-pushing surfaceof pressure behind the IJ22, IJ23, IJ25, pushing the actuator betweenpaddle IJ28, IJ31, IJ32, surface the inlet and the IJ33, IJ34, IJ35,nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off so that the motion of achieved the inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to ink Silverbrook, EPactuator of ink jet, there is no problem is back-flow on 0771 658 A2 anddoes not expansion or eliminated actuation related patent result inmovement of an applications ink back- actuator which may Valve-jet flowcause ink back-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are No added May not be Most ink jet systemsnozzle fired periodically, complexity on the sufficient to IJ01, IJ02,IJ03, firing before the ink has a print head displace dried ink IJ04,IJ05, IJ06, chance to dry. When IJ07, IJ09, IJ10, not in use the nozzlesIJ11, IJ12, IJ14, are sealed (capped) IJ16, IJ20, IJ22, against air.IJ23, IJ24, IJ25, The nozzle firing is IJ26, IJ27, IJ28, usuallyperformed IJ29, IJ30, IJ31, during a special IJ32, IJ33, IJ34, clearingcycle, after IJ36, IJ37, IJ38, first moving the print IJ39, IJ40, IJ41,head to a cleaning IJ42, IJ43, IJ44, station. IJ45 Extra In systemswhich heat Can be highly Requires higher Silverbrook, EP power to theink, but do not boil effective if the drive voltage for 0771 658 A2 andink heater it under normal heater is adjacent to clearing related patentsituations, nozzle the nozzle May require larger applications clearingcan be drive transistors achieved by over- powering the heater andboiling ink at the nozzle. Rapid The actuator is fired in Does notrequire Effectiveness May be used with: succession rapid succession. Inextra drive circuits depends IJ01, IJ02, IJ03, of some configurations,on the print head substantially upon IJ04, IJ05, IJ06, actuator this maycause heat Can be readily the configuration of IJ07, IJ09, IJ10, pulsesbuild-up at the nozzle controlled and the ink jet nozzle IJ11, IJ14,IJ16, which boils the ink, initiated by digital IJ20, IJ22, IJ23,clearing the nozzle. In logic IJ24, IJ25, IJ27, other situations, it mayIJ28, IJ29, IJ30, cause sufficient IJ31, IJ32, IJ33, vibrations todislodge IJ34, IJ36, IJ37, clogged nozzles. IJ38, IJ39, IJ40, IJ41,IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple solution Notsuitable where May be used with: power to not normally driven to whereapplicable there is a hard limit IJ03, IJ09, IJ16, ink the limit of itsmotion, to actuator IJ20, IJ23, IJ24, pushing nozzle clearing may bemovement IJ25, IJ27, IJ29, actuator assisted by providing IJ30, IJ31,IJ32, an enhanced drive IJ39, IJ40, IJ41, signal to the actuator. IJ42,IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle High IJ08,IJ13, IJ15, resonance applied to the ink clearing capabilityimplementation cost IJ17, IJ18, IJ19, chamber. This wave is can beachieved if system does not IJ21 of an appropriate May be alreadyinclude an amplitude and implemented at very acoustic actuator frequencyto cause low cost in systems sufficient force at the which alreadynozzle to clear include acoustic blockages. This is actuators easiest toachieve if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear severely AccurateSilverbrook, EP clearing plate is pushed against clogged nozzlesmechanical 0771 658 A2 and plate the nozzles. The plate alignment isrelated patent has a post for every required applications nozzle. A postmoves Moving parts are through each nozzle, required displacing driedink. There is risk of damage to the nozzles Accurate fabrication isrequired Ink The pressure of the ink May be effective Requires pressureMay be used with pressure is temporarily where other pump or other allIJ series ink jets pulse increased so that ink methods cannot bepressure actuator streams from all of the used Expensive nozzles. Thismay be Wasteful of ink used in conjunction with actuator energizing.Print head A flexible ‘blade’ is Effective for planar Difficult to useif Many ink jet wiper wiped across the print print head surfaces printhead surface is systems head surface. The Low cost non-planar or veryblade is usually fragile fabricated from a Requires flexible polymer,e.g. mechanical parts rubber or synthetic Blade can wear out elastomer.in high volume print systems Separate A separate heater is Can beeffective Fabrication Can be used with ink boiling provided at thenozzle where other nozzle complexity many IJ series ink heater althoughthe normal clearing methods jets drop e-ection cannot be used mechanismdoes not Can be implemented require it. The heaters at no additionalcost do not require in some ink jet individual drive configurationscircuits, as many nozzles can be cleared simultaneously, and no imagingis required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages ExamplesElectroformed A nozzle plate is Fabrication High temperatures HewlettPackard nickel separately fabricated simplicity and pressures areThermal Ink jet from electroformed required to bond nickel, and bondedto nozzle plate the print head chip. Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks requiredEach hole must be Canon Bubblejet ablated or holes are ablated by an Canbe quite fast individually formed 1988 Sercel et al., drilled intense UVlaser in a Some control over Special equipment SPIE, Vol. 998 polymernozzle plate, which is nozzle profile is required Excimer Beam typicallya polymer possible Slow where there Applications, pp. such as polyimideor Equipment required are many thousands 76-83 polysulphone isrelatively low cost of nozzles per print 1993 Watanabe et head al., U.S.Pat. No. 5,208,604 May produce thin burrs at exit holes Silicon Aseparate nozzle High accuracy is Two part K. Bean, IEEE micromachinedplate is attainable construction Transactions on micromachined from Highcost Electron Devices, single crystal silicon, Requires precision Vol.ED-25, No. 10, and bonded to the alignment 1978, pp 1185-1195 print headwafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins et al.,U.S. Pat. No. 4,899,181 Glass Fine glass capillaries No expensive Verysmall nozzle 1970 Zoltan U.S. Pat. No. capillaries are drawn from glassequipment required sizes are difficult to 3,683,212 tubing. This methodSimple to make form has been used for single nozzles Not suited for massmaking individual production nozzles, but is difficult to use for bulkmanufacturing of print heads with thousands of nozzles. Monolithic, Thenozzle plate is High accuracy (<1 μm) Requires sacrificial Silverbrook,EP surface deposited as a layer Monolithic layer under the 0771 658 A2and micromachined using standard VLSI Low cost nozzle plate to formrelated patent using VLSI deposition techniques. Existing processes thenozzle chamber applications lithographic Nozzles are etched in can beused Surface may be IJ01, IJ02, IJ04, processes the nozzle plate usingfragile to the touch IJ11, IJ12, IJ17, VLSI lithography and IJ18, IJ20,IJ22, etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34,IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, Thenozzle plate is a High accuracy (<1 μm) Requires long etch IJ03, IJ05,IJ06, etched buried etch stop in the Monolithic times IJ07, IJ08, IJ09,through wafer. Nozzle Low cost Requires a support IJ10, IJ13, IJ14,substrate chambers are etched in No differential wafer IJ15, IJ16, IJ19,the front of the wafer, expansion IJ21, IJ23, IJ25, and the wafer isIJ26 thinned from the back side. Nozzles are then etched in the etchstop layer. No nozzle Various methods have No nozzles to Difficult tocontrol Ricoh 1995 Sekiya plate been tried to eliminate become cloggeddrop position et al U.S. Pat. No. 5,412,413 the nozzles entirely, toaccurately 1993 Hadimioglu et prevent nozzle Crosstalk problems al EUP550,192 clogging. These 1993 Elrod et al include thermal bubble EUP572,220 mechanisms and acoustic lens mechanisms Trough Each drop ejectorhas Reduced Drop firing IJ35 a trough through manufacturing direction issensitive which a paddle moves. complexity to wicking. There is nonozzle Monolithic plate. Nozzle slit The elimination of No nozzles toDifficult to control 1989 Saito et al instead of nozzle holes and becomeclogged drop position U.S. Pat. No. 4,799,068 individual replacement bya slit accurately nozzles encompassing many Crosstalk problems actuatorpositions reduces nozzle clogging, but increases crosstalk due to inksurface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesEdge Ink flow is along the Simple construction Nozzles limited to CanonBubblejet (‘edge surface of the chip, No silicon etching edge 1979 Endoet al GB shooter’) and ink drops are required High resolution is patent2,007,162 ejected from the chip Good heat sinking difficult Xeroxheater-in-pit edge. via substrate Fast color printing 1990 Hawkins et alMechanically strong requires one print U.S. Pat. No. 4,899,181 Ease ofchip head per color Tone-jet handing Surface Ink flow is along the Nobulk silicon Maximum ink flow Hewlett-Packard TIJ (‘roof surface of thechip, etching required is severely restricted 1982 Vaught et alshooter’) and ink drops are Silicon can make an U.S. Pat. No. 4,490,728ejected from the chip effective heat sink IJ02, IJ11, IJ12, surface,normal to the Mechanical strength IJ20, IJ22 plane of the chip. ThroughInk flow is through the High ink flow Requires bulk Silverbrook, EPchip, chip, and ink drops are Suitable for silicon etching 0771 658 A2and forward ejected from the front pagewidth print related patent (‘upsurface of the chip. heads applications shooter’) High nozzle packingIJ04, IJ17, IJ18, density therefore IJ24, IJ27-IJ45 low manufacturingcost Through Ink flow is through the High ink flow Requires wafer IJ01,IJ03, IJ05, chip, chip, and ink drops are Suitable for thinning IJ06,IJ07, IJ08, reverse ejected from the rear pagewidth print Requiresspecial IJ09, IJ10, IJ13, (‘down surface of the chip. heads handlingduring IJ14, IJ15, IJ16, shooter’) High nozzle packing manufacture IJ19,IJ21, IJ23, density therefore IJ25, IJ26 low manufacturing cost ThroughInk flow is through the Suitable for Pagewidth print Epson Stylusactuator actuator, which is not piezoelectric print heads requireTektronix hot melt fabricated as part of heads several thousandpiezoelectric ink jets the same substrate as connections to drive thedrive transistors. circuits Cannot be manufactured in standard CMOS fabsComplex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Waterbased ink which Environmentally Slow drying Most existing ink dyetypically contains: friendly Corrosive jets water, dye, surfactant, Noodor Bleeds on paper All IJ series ink jets humectant, and Maystrikethrough Silverbrook, EP biocide. Cockles paper 0771 658 A2 andModern ink dyes have related patent high water-fastness, applicationslight fastness Aqueous, Water based ink which Environmentally Slowdrying IJ02, IJ04, IJ21, pigment typically contains: friendly CorrosiveIJ26, IJ27, IJ30 water, pigment, No odor Pigment may clog Silverbrook,EP surfactant, humectant, Reduced bleed nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may clog related patent Pigments havean Reduced actuator applications advantage in reduced strikethroughmechanisms Piezoelectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink jets Ethylvolatile solvent used Prints on various Flammable Ketone for industrialprinting substrates such as (MEK) on difficult surfaces metals andplastics such as aluminum cans. Alcohol Alcohol based inks Fast dryingSlight odor All IJ series ink jets (ethanol, can be used where theOperates at sub- Flammable 2-butanol, printer must operate at freezingand temperatures below temperatures others) the freezing point ofReduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- ink High viscosity Tektronix hot melt change room temperature, andinstantly freezes on Printed ink typically piezoelectric ink jets (hotmelt) is melted in the print the print medium has a ‘waxy’ feel 1989Nowak U.S. Pat. No. head before jetting. Almost any print Printed pagesmay 4,820,346 Hot melt inks are medium can be used ‘block’ All IJ seriesink jets usually wax based, No paper cockle Ink temperature with amelting point occurs may be above the around 80° C. After No wickingoccurs curie point of jetting the ink freezes No bleed occurs permanentmagnets almost instantly upon No strikethrough Ink heaters consumecontacting the print occurs power medium or a transfer Long warm-up timeroller. Oil Oil based inks are High solubility High viscosity: this AllIJ series ink jets extensively used in medium for some is a significantoffset printing. They dyes limitation for use in have advantages in Doesnot cockle ink jets, which improved paper usually require acharacteristics on Does not wick low viscosity. Some paper (especiallyno through paper short chain and wicking or cockle). multi-branched oilsOil soluble dies and have a sufficiently pigments are required. lowviscosity. Slow drying Microemulsion A microemulsion is a Stops inkbleed Viscosity higher All IJ series ink jets stable, self forming Highdye solubility than water emulsion of oil, water, Water, oil, and Costis slightly and surfactant. The amphiphilic soluble higher than watercharacteristic drop size dies can be used based ink is less than 100 nm,Can stabilize High surfactant and is determined by pigment concentrationthe preferred curvature suspensions required (around of the surfactant.5%)

1. A printhead for an inkjet printer, the printhead having a pluralityof micro-electromechanical ejection mechanisms arranged in a wafersubstrate, each mechanism comprising: chamber walls and a roof formed onsaid substrate to define an ink chamber, one wall defining a slottherein, and an ink supply channel defined through the substrate to saidchamber; and a bi-layer thermal actuator coil fast with the substrateand ending in a strut extending through the slot, said strut fast with apaddle device within the chamber.
 2. The printhead as claimed in claim1, wherein the bi-layer actuator coil includes a first layermanufactured from a non-conductive material and a second layermanufactured from a conductive material.
 3. The printhead as claimed inclaim 2, wherein the first layer is manufactured from glass and thesecond layer is manufactured from titanium diboride.
 4. The printhead asclaimed in claim 3, wherein the substrate includes a CMOS layer arrangedin electrical communication with the second layer.
 5. The printhead asclaimed in claim 1, wherein the strut and slot are treated to behydrophobic.
 6. The printhead as claimed in claim 1, wherein the roofdefines an ejection rim portion configured to exploit surface tensioncharacteristics of ink in the chamber to prevent ink from flowing out ofthe chamber.
 7. The printhead as claimed in claim 1, wherein the slot isshaped and dimensioned so that surface tension characteristics of theink assist in preventing ink from flowing out of the slot.